A conventional bite valve has a resilient sheath and a main body. The sheath has an opening on one end through which liquid passing through the main body can be expelled. The other end of the sheath is affixed to the main body. Within the sheath is a seal rod and a biasing member such as a compression spring. The biasing member supplies a force that urges the end of the seal rod into the opening of the sheath. That end of the seal rod is shaped to fill that opening and provide a seal that helps prevent liquid from escaping through the bite valve. The seal rod is configured so that when a user bites down on the sheath, the sheath compresses into the seal rod forcing the seal rod into the main body. Sufficient bite pressure overcomes the biasing member. This causes the end of the seal rod to disengage from the sheath's opening, thus allowing liquid to pass through the main body and out the opening. US Pub. 2007/0164037 to Chen describes such a conventional bite valve.
When such a bite valve is coupled to a pressurized source, maintaining a proper seal is desirable. Through use and time, the sheath's opening can deform resulting in a poor or inoperative seal allowing undesired leaking.